The present invention relates to optically active compounds which are used as optically active compounds such as physiological active compounds, functional materials and so on, and a process for producing thereof.
Compounds represented by the general formula: ##STR3## wherein R.sup.1, R.sup.2 and R.sup.3 are selected from alkyl groups having 1-4 carbon atoms and phenyl groups, X is selected from a hydrogen atom ##STR4## and R is selected from alkyl groups having 1-20 carbon atoms, have not been known as optically active compounds, but as racemates. The compounds represented by the above general formula (II) are useful chemical compounds as starting materials for pharmaceuticals, agricultural chemicals and the like, and as intermediates. However, the compounds have optical isomers, and in many cases they do not sufficiently exhibit their useful characteristics because they are not obtained as pure compounds. Accordingly, it has been required to obtain preponderantly pure R- or S-compounds.
For the above reasons, and in order to obtain an optically active substance, it is necessary to optically resolve a racemate (itself typically obtained by a synthetic chemical technique), to conduct an asymmetric synthesis, or to convert from an optically active starting material by a stereochemical synthetic method. In many cases, the process is troublesome and disadvantageous industrially.
Similar compounds to the above compounds represented by the general formula (II) are synthesized as starting materials of prostaglandin (M. Nishizawa, M. Yamada and R. Noyori, Tetrahedron Letters, 22, 247(1981)). However, alkyl chains of the compounds of the present invention are different from those of the above compounds, so that the optically active compounds of the present invention have not been obtained by the conventional methods.
Accordingly, it is desired to develop a technique for obtaining optically active compounds of the present invention by an industrially advantageous method.